Three-terminal MRAM with ac write-assist for low read disturb

Patent metadata

Field	Value
Publication number	US-10199083-B1
Application number	US-201715859047-A
Country	US
Kind code	B1
Filing date	Dec 29, 2017
Priority date	Dec 29, 2017
Publication date	Feb 5, 2019
Grant date	Feb 5, 2019

Abstract

Methods and structures useful for magnetoresistive random-access memory (MRAM) are disclosed. The MRAM device has a magnetic tunnel junction stack having a significantly improved performance of the free layer in the magnetic tunnel junction structure. The MRAM device also utilizes a three-terminal structure, thereby allowing efficient writing of the bit without a concomitant increase in read disturb.

First claim

What is claimed is:

1. A magnetic device comprising:
a reference magnetic layer in a first plane, the reference magnetic layer having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;
a non-magnetic tunnel barrier layer in a second plane and disposed over the reference magnetic layer;
a free magnetic layer in a third plane and disposed over the non-magnetic tunnel barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the third plane and having a magnetization direction that can switch from a first magnetization direction to a second magnetization direction and from the second magnetization direction to the first magnetization direction, with a switching process that involves precessions at a precession radius around an axis perpendicular to the third plane, the magnetization vector of the free magnetic layer having a predetermined precession frequency, the reference magnetic layer, the non-magnetic tunnel barrier layer and the free magnetic layer forming a magnetic tunnel junction;
a non-magnetic spacer in a fourth plane and disposed over the free magnetic layer;
an in-plane polarization magnetic layer in a fifth plane disposed over the non-magnetic spacer, the in-plane polarization magnetic layer having a magnetization vector that is parallel to the fifth plane;
a non-magnetic insulator adjacent to the non-magnetic spacer and the in-plane polarization magnetic layer;
a metallic terminal coupled to the magnetic tunnel junction and adjacent to the non-magnetic insulator, the metallic terminal separated from the non-magnetic spacer and the in-plane polarization magnetic layer by the non-magnetic insulator;
a first current source that directs a read current through the metallic terminal and the magnetic tunnel junction, wherein the read current measures the resistance across the magnetic tunnel junction; and
a second current source that directs a programming current pulse through the magnetic tunnel junction, the non-magnetic spacer, and the in-plane polarization magnetic layer, the programming current pulse comprising a direct current pulse and an alternating perturbation pulse, the alternating perturbation pulse alternating between a maximum current value and a minimum current value at a first frequency;
wherein application of the programming current pulse to the magnetic device produces a spin-polarized current having spin-polarized electrons, the spin-polarized current alternating between a maximum spin-current value and a minimum spin-current value at the first frequency, the spin-polarized electrons exerting a spin transfer torque on the magnetization vector of the free magnetic layer, the spin transfer torque alternating between a maximum magnitude and a minimum magnitude at the first frequency;
wherein the first frequency is synchronized with the predetermined precession frequency of the free magnetic layer, thereby causing the spin transfer torque to be at the maximum magnitude when the spin transfer torque increases the precession radius of the magnetization vector of the free magnetic layer, and at the minimum magnitude when the spin transfer torque decreases the precession radius of the magnetization vector of the free magnetic layer, thereby improving the switching process of the free magnetic layer from the first magnetization direction to the second magnetization direction and from the second magnetization direction to the first magnetization direction.

2. The magnetic device of claim 1 , wherein a difference in frequency between the first frequency and the predetermined precession frequency of the free magnetic layer is less than twenty percent of the predetermined precession frequency of the free magnetic layer.

3. The magnetic device of claim 1 , wherein a difference in frequency between the first frequency and the predetermined precession frequency of the free magnetic layer is less than ten percent of the predetermined precession frequency of the free magnetic layer.

4. The magnetic device of claim 1 , wherein a difference in frequency between the first frequency and the predetermined precession frequency of the free magnetic layer is less than five percent of the predetermined precession frequency of the free magnetic layer.

5. The magnetic device of claim 1 , wherein a difference in frequency between the first frequency and the predetermined precession frequency of the free magnetic layer is less than two percent of the predetermined precession frequency of the free magnetic layer.

6. The magnetic device of claim 1 , wherein the direct current pulse has a current value different than zero.

7. The magnetic device of claim 1 , wherein the direct current pulse has a value that is fixed throughout the duration of the pulse.

8. The magnetic device of claim 1 , wherein the magnetization vector of the in-plane polarization magnetic layer is fixed.

9. The magnetic device of claim 1 , wherein the metallic terminal comprises a metal, a metallic nanofiber, or a conductive carbon nanotube.

10. The magnetic device of claim 1 , wherein the reference magnetic layer comprises CoFeB, the non-magnetic tunnel barrier layer comprises MgO, the free magnetic layer comprises CoFeB, the non-magnetic spacer comprises MgO, and the in-plane polarization magnetic layer comprises CoFeB.

11. A magnetic device comprising:
a reference magnetic layer in a first plane, the reference magnetic layer having a magnetization vector that is perpendicular to the first plane and having a fixed magnetization direction;
a non-magnetic tunnel barrier layer in a second plane and disposed over the reference magnetic layer;
a free magnetic layer in a third plane and disposed over the non-magnetic tunnel barrier layer, the free magnetic layer having a magnetization vector that is perpendicular to the third plane and having a magnetization direction that can switch from a first magnetization direction to a second magnetization direction and from the second magnetization direction to the first magnetization direction, with a switching process that involves precessions around an axis perpendicular to the third plane, the reference magnetic layer, the non-magnetic tunnel barrier layer and the free magnetic layer forming a magnetic tunnel junction (MTJ);
a non-magnetic spacer in a fourth plane and disposed over the free magnetic layer;
an in-plane polarization magnetic layer in a fifth plane and disposed over the non-magnetic spacer, the in-plane polarization magnetic layer having a magnetization vector that is parallel to the fifth plane;
a metallic spacer in a sixth plane and disposed over the in-plane polarization magnetic layer;
an in-plane spin torque oscillator layer in a seventh plane and disposed over the metallic spacer, the in-plane spin torque oscillator layer having a magnetization vector that precesses around an in-plane anisotropy axis upon application of a programming voltage;
a non-magnetic spin torque oscillator barrier layer in an eighth plane and disposed over the in-plane spin torque oscillator layer;
a perpendicular spin torque oscillator layer in a ninth plane and disposed over the non-magnetic spin torque oscillator barrier layer, the perpendicular spin torque oscillator layer having a magnetization vector that precesses around an out-of-plane anisotropy axis upon application of the programming voltage, the non-magnetic spin torque oscillator barrier layer, the in-plane spin torque oscillator layer, the non-magnetic spin torque oscillator barrier layer, and the perpendicular spin torque oscillator layer forming a spin torque nano oscillator (STNO);
a non-magnetic insulator adjacent to the non-magnetic sp

Assignees

• Spin Transfer Tech Inc

Inventors

• Bozdag Kadriye Deniz
• GAJEK Marcin Jan
• Tzoufras Michail
• Ryan Eric Michael

Classifications

• H01L43/10

  Electricity · mapped topic

• H01L43/02

  Electricity · mapped topic

• G11C11/1675

  Writing or programming circuits or methods · CPC title

• H01L27/226

  Electricity · mapped topic

• B82Y25/00

  Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance · CPC title